The increasing need for high recording area densities (up to 500 Gb/in2) is making the perpendicular magnetic recording head (PMR head) a replacement of choice for the longitudinal magnetic recording head (LMR head).
In fully wrapped-around shielded (FWAS) PMR writer heads, a continuous shield surrounding the pole provides a continuous magnetic flux from leading shield (LS) to side shield (SS). In order to achieve a seamless interface between the leading shield and side shield block, an appropriate pre-etch step is adopted to provide a clean surface on leading shield before side shield seed deposition. But the re-entrant shape of pole and surrounding structures produces a shadowing effect which makes it extremely difficult for a standard parallel plate etching technique such as the sputter etching to reach and clean the target SS deposition area around the pole, especially in the bottom corner of the pole.
FIGS. 1A-C are figures that illustrate the aforementioned shadow effects. FIG. 1A is a diagram depicting a top view of a target side shield (SS) deposition area around a pole. FIG. 1B is a diagram depicting a cross-sectional view of the target SS deposition area along the cross-section A indicated in FIG. 1A. FIG. 1B illustrates the shadowed or “black line” location on the leading bevel. FIG. 1C is a diagram depicting a cross-sectional view of the target SS deposition area along the cross-section B indicated in FIG. 1A. FIG. 1C likewise illustrates the black line location on the leading bevel.
As illustrated in FIGS. 1B and C, the black line to be removed is trapped in the deep bottom of a well which is surrounded by the overhang above the main pole, inclined side gap, and leading bevel slope, which present a formidable obstacle to providing a clean interface between the LS and the SS. This is especially true since sputter etching, which is traditionally used for cleaning the LS-SS interface, has no wafer tilt function to circumvent the shadowing effect. Accordingly, only the surface at open field can be effectively cleaned by the sputter etch with the dark line remaining at the corner areas. The presence of the dark line compromises the structural integrity and/or produces a magnetic discontinuity between the LS and SS regions, which in turn can cause adjacent track interference (ATI) issues in the resulting FWAS PMR writer pole.